First of all, your variable declaration is not right. There must be no spaces around = in declaration:

myDir='apple'

Now, ls /home/$myDirfruit did not work because myDirfruit is being treated as the variable name instead of just myDir. You need to use {} to enclose the variable name when the name is being followed by valid variable name constituent character:

ls /home/${myDir}fruit

would be expanded to:

ls /home/applefruit

Also if you have spaces in variable name e.g. myDir='foo bar', use quotes around variable: